PLANT-SOIL IN1ERACTIONS AT LOW pH: PRINCIPLES AND MANAGEMENT

Developments in Plant and Soil Sciences

VOLUME 64

The titles published in this series are listed at the end of this volume.

Plant-Soil Interactions at Low pH: Principles and Management

Proceedings of the Third International Symposium on Plant-Soil Interactions at Low pH, Brisbane, Queensland, Australia, 12-16 September 1993

Edited by

R.A. DATE, N.J. GRUNDON, G.E. RAYMENT and M.E. PROBERT

Partly reprinted from Plant and Soi!, Volume 171, No. 1 (1995)

u

" SPRINGER-SCIENCE+BUSINESS MEDIA, B.V.

A C.I.P. Cata10gue record for this book is availab1e from the Library of Congress.

ISBN 978-94-010-4099-0 ISBN 978-94-011-0221-6 (eBook) DOI 10.1007/978-94-011-0221-6

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AH Rights Reserved © 1995 Springer Science+Business Media Dordrecht Originally published by Kluwer Academic Publishers in 1995 Softcover reprint ofthe hardcover Ist edition 1995

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Contents

Preface

OVERVIEW PAPER

*1. Global extent, development and economic impact of acid soils H.R. von UexkUll, E. Mutert

SECTION I: CHEMISTRY AND PHYSICS OF ACID SOILS

*2. Soluble aluminium in acidic soils: Principles and practicalities

1

5

G.S.P. Ritchie 23

3. Potential solid phases controlling dissolved aluminium and iron concentrations in acidic soils K.J. Reddy, L. Wang, S.P. Gloss 35

4. Amelioration of aluminium phytotoxicity with organic matter M.T.F. Wong, R.S. Swift 41

*5. Chromatographic techniques for the separation of Al and associated organic ligands present in soil solution G.L. Kerven, Z. Ostatek-Boczynski, D.G. Edwards, C.J. Asher, J. Oweczkin 47

*6. Quantitative 27 Al NMR spectroscopic studies of Al (III) complexes with organic acid ligands and their comparison with GEOCHEM predicted values G.L. Kerven, P.L. Larsen, L.C. Bell, D.G. Edwards 53

*7. Aluminium reactions with polygalacturonate and related organic ligands Z. Ostatek-Boczynski, G.L. Kerven, F.P.c. Blarney 59

8. Forms of extractable aluminium in Canadian acid soils and their relations to plant growth Y.K. Soon 65

9. Phenolic acids in boreal peats from Finland and comparison with those from tropical and temperate areas T. Katase 71

10. Rates and sources of acidification in agriculatural systems of southern Australia W.M. Porter, C.D.A. McLay, P.J. Dolling 75

11. Effects of long-term application of phosphate fertilisers on soil acidity under pasture in New Zealand V. Manoharan, P. Loganathan, R.W. Tillman 85

*Chapters indicated with an asterisk are reprinted from Plant and Soil Volume 171, No. 1 (1995).

VI Contents

12. A model for understanding the importance of various chemical, physical and biological processes in the development of soil profile acidity J.B. Robinson, K.R. Helyar, Z. Hochman 93

*13. Models for relating pH measurements in water and calcium chloride for a wide range of pH, soil types and depths C.R. Ahem, D.E. Baker, R.L. Aitken 99

14. Long-term effects of ammonium nitrate application on soil pH, and micronutrients in soil and bromegrass hay S.S. Malhi, M. Nyborg, J.T. Harapiak, DJ. Heaney 105

15. Nitrogen mineralisation and nitrification in acidic subsurface layers of soil S.R. Young, A.S. Black, M.K. Conyers 111

16. Reactions buffering pH in acid soils treated with lime K.R. Helyar, M.K. Conyers, A.M. Cowling 117

17. Phosphorus sorption of coal-mine soils in Galicia, NW Spain M.L. Fernandez Marcos, E. Alvarez Rodriguez, C. Monterroso 125

18. Quantity/intensity relation and phosphorus availability in south Brazilian latosols as affected by form and placement of phosphorus and farmyard manure W. Werner, E.E. Scherer 129

19. The effect of flooding on S sorption capacity and ABC of variable charge soils A. Triana, R.D.B. Lefroy, GJ. Blair 135

*20. Solubility and mobility of copper, zinc and lead in acidic environments KJ. Reddy, L. Wang, S.P. Gloss 141

21. Acid surface soil distribution and extent in Queensland, Australia C.R. Ahem, R.F. Isbell, M.M.G. Weinand 147

22. Does climate influence the pH of Queensland surface soils? C.R. Ahem, M.M.G. Wein 155

*23. Influence of acid rain and ozone on soil heavy metals under loblolly pine trees: A field study P.A. Nouri, G.B. Reddy 161

SECTION 2: MICROBIAL AND FAUNAL ACTIVITY IN ACID SOILS

24. Microbial activity in acid soils J.M. Lynch 167

*25. A mechanism of aluminium toxicity to soil bacteria and possible ecological implications M. Wood 173

*26. Characteristics of an ideotype acid tolerant pasture legume symbiosis in Mediterranean agriculture J.G. Howieson 181

Contents VII

27. Effect of pH on nitrogenase activity and mineral composition of Medicago truncatula cv. Jamalong and M. polymorpha cv. Serena inoculated with Rhizobium meliloti Y. Lestari, A.H. Gibson, R.D. Graham 187

28. Effects of excess aluminium and manganese on growth and phosphorus nutrition of mycorrhizal sorghum grown under acidic conditions C.A.B. Medeiros, R.B. Clark, J.R. Ellis 193

29. Faunal activity in acid soils P. Lavelle, A. Chauvel, C. Fragoso 201

30. Abundance of earthworms in soils used for cereal production in south-eastern Australia and their role in reducing soil acidity G.H. Baker, V.I. Barrett, P.I. Carter, J.C. Buckerfield, P.M.L. Williams, G.P. Kilpin 213

SECTION 3: MECHANISMS OF ACID TOLERANCE OF PLANTS

31. Techniques for assessing plant responses on acid soils D.C. Edmeades, F.P.c. Blamey, M.P.W. Farina 221

32. Adaptation of tropical forage species to acid soils: the influence of varying phosphorus supply and soil type on plant growth I.M. Rao, V. Borrero, M.A. Ayarza, R. Garcia 235

*33. Tolerance and avoidance of Al toxicity by Mucuna pruriens var. utilis at different levels ofP supply K. Hairiah, M. van Noordwijk, S. Setijono 243

* 34. Tolerance of Australian tropical and subtropical Acacias to acid soil N. Ashwath, P.I. Dart, D.G. Edwards, P.K. Khanna 249

*35. Overcoming barriers to understanding the cellular basis of aluminium resistance G.I. Taylor 255

*36. Plasma membrane of younger and outer cells is the primary specific site for aluminium toxicity in roots T. Wagatsuma, S. Ishikawa, H. Obata, K. Tawaraya, S. Katohda 271

*37. Effect of aluminium on membrane properties of soybean (Glycine max) cells in suspension culture A. StaB, W.I. Horst 279

*38. Involvement of plasma membrane potential in the tolerance mechanism of plant roots to aluminium toxicity M. Sasaki, M. Kasai, Y. Yamamoto, H. Matsumoto 285

*39. Transmembrane calcium fluxes during Al stress Z. Rengel, M. Pmeros, M. Tester 291

• 40. Aluminium and calcium transport interactions in intact roots and root plasmalemma vesicles from aluminium-sensitive and tolerant wheat cultivars J.w. Huang, D.L. Grunes, L.V. Kochian 297

VIII Contents

* 41. Antagonism between aluminium and calcium for sorption by calcium pectate F.P.c. Blamey, AJ. Dowling 303

* 42. Magnesium uptake by AL-stressed maize plants with special emphasis on cation interactions at root exchange sites w.G. Keltjens 307

*43. Analysis of acid-soil stress in sorghum genotypes with emphasis on aluminium and magnesium interactions K. Tan, w.G. Keltjens 313

* 44. Root growth analysis: An underutilised approach to understanding aluminium rhizotoxicity D.R. Parker 317

* 45. The effect of aluminium concentration on root hairs in white clover (Trifolium repens L.) D.A. Care 325

* 46. Physiological response of root tip of alfalfa to low pH and aluminium stress in water culture S. Yokota, K. Ojima 329

* 47. Ultrastructural investigations and EDX-analyses of AI-treated oat (Avena sativa) roots S. Marienfeld, H. Lehmann, R. Stelzer 333

48. Increase of ATP-dependent H+ pump activity of tonoplast of barley roots by aluminium stress: Possible involvement of abscisic acid for the regulation M. Kasai, M. Sasaki, K. Yamashita, Y. Yamamoto, H. Matsumoto 341

*49. Solution pH modifies the response of Norway spruce seedlings to aluminium D.L. Godbold, G. Jentschke, P. Marschner 345

50. Effect of nitrogen source and aluminium on the growth of two wheat cultivars known to differ in aluminium tolerance D.M. Wheeler 349

* 51. Characteristics of carrot plant regenerated from two cell line selected as either ionic-AI tolerant cell or AI-phosphate utilizing cells H. Koyama, K. Ojima, T. Yamaya, Y. Sonoda 353

52. Determining factors for aluminium toxicity in cultured tobacco cells: medium components and cellular growth conditions Y. Yamamoto, K. Ono, H. Matsumoto 359

53. Aluminium tolerance caused by phosphate starvation in cultured tobacco cells Y. Yamamoto, K. Mametsuka, B. Ezaki, H. Matsumoto 363

54. Phytotoxicity of monomer aluminium ions and hydroxy-aluminium polymer ions in an Andosol Masahiko Saigusa, Toru Matsumoto, Tokuro Abe 367

55. Performance of soybean cultivars at different concentrations of manganese in nutrient solution H.A.A. Mascarenhas, R.T. Tanaka, M.A.C. Miranda, V. Nagai, Q.A. de C. Carmello 371

Contents IX

* 56. Cadmium and copper interactions on the accumulation and distribution of Cd and Cu in birch (Betula pendula Roth) seedlings M. Gussarsson, S. Adalsteinsson, P. Jensen, H. Asp 375

57. Physiological state of shoots and roots and of energy transformation systems in plants at low pH N.V. Budagovskaya 379

58. Regulation of electrogenesis of root cells at low pH V.D. Gajiyev, V.M. Ali-Zade, T.S. Akhundova, EK. Aliyeva, R.A. Gasanov 385

SECTION 4: SELECTION AND BREEDING OF ACID TOLERANT PLANTS

59. Advances in the selection and breeding of acid-tolerant plants: rice, maize, sorghum and tropical forages R.S. Zeigler, S. Pandey, J. Miles, L.M. Gourley, S. Sarkarung 391

60. Use of improved tolerant cultivars to increase rice production on acid histosols of southern Sri Lanka P.A.N. Chandrasiri, R. Pathirana 407

61. Response of rice cultivars to increased iron and aluminium concentrations R. Pathirana, P.A.N. Chandrasiri, S.G. Sirisena 413

62. Progress from selection for tolerance to soil acidity in five tropical maize populations H. Ceballos, S. Pandey, E.B. Knapp, J. Duque 419

63. Soil acidity effects on agribotanical traits of durum and common wheat L. Bona, V.C. Baligar, R.I. Wright 425

64. A proposal for a working group on acid soil tolerance in grain legumes R.C. Nageswara Rao, C.L.L. Gowda, C. Johansen, O.P. Rupela, A.K. Singh, S.N. Nigam, M.M. 429 Anders, T.I. Rego, D. McDonald

65. The effect of aluminium on the growth of a range of temperate legume species and cultivars: A summary of results D.M. Wheeler, M.B. Dodd 433

66. Chemical content of AI-tolerant and AI-susceptible breeding lines of white clover J.R. Caradus, A.D. Mackay 439

67. Distribution of AI-tolerance in crosses between genotypes of white clover selected for either AI­tolerance or AI-susceptibility J.R. Caradus, A.D. Mackay 447

68. In vitro selection for aluminium tolerance in red clover (Trifolium pratense L.) W. Pawlowski, B. Skucinska 451

69. Improving the acid-soil tolerance of Medicago sativa by asymmetric somatic hybridisation P.A. Stoutjesdijk, PJ. Larkin, P.W.G. Sale 455

X Contents

70. Quantitative genetic variation for acid soil tolerance in a Phalaris aquatica x P. arundinacea x P. aquatica backcross population R.N. Oram, A.M. Ridley 459

SECTION 5: DIAGNOSIS AND CORRECTION OF ACID SOIL INFERTILITY

71. Acidification of sub-surface soils under pastures in Victoria, Australia D.M. Crawford, C.D. Parnell, J. Maheswaran 467

72. Soil acidification under pastures of north-eastern Victoria five years after liming A.M. Ridley, D.R. Coventry 473

73. Field calibration of lime requirement soil tests R.L. Aitken, P.w. Moody, T. Dickson 479

74. Modified lime requirement for South African sugar belt soils based on an aluminium to sulphur ratio B.L. Schroeder, J.H. Meyer, R.A. Wood 485

75. Agronomic efficiency of limestones with different acid-neutralizing capacity, under field condition J.A. Quaggio, P.B. Gallo, H.A.A. Mascarenhas 491

76. Evaluation of liming materials used in South Australia R.H. Merry, TJ.V. Hodge, D.C. Lewis, J. Jacka 497

77. Limestone efficiency and boron effects on forage yield and soil properties V.A. Haby, R.H. Loeppert, R. Villavicencio, A.T. Leonard, J.V. Davis 505

78. Residual effects of dolomitic limestone on com grown on an acidic Malaysian Ultisol H.A.H. Sharifuddin, J. Shamshuddin, NJ. Grundon, D.G. Edwards, A.R. Zaharah 511

79. Effects of coal flue gas desulfurisation by-products and calcium-sulfite, -sulfate and -carbonate on maize grown in acid soil R.B. Clark, S.K. Zeto, K.D. Ritchey, R.R. Wendell, V.C. Baligar 519

80. Effect of gypsum application rate and leaching regime on wheat growth in a highly acidic subsoil C.D.A. McLay, G.S.P. Ritchie 527

81. Efficiency of surface-applied ameliorants for alleviating acidity in two vineyard soil types WJ. Conradie 531

82. Diagnosis of maize yield response to lime in some weathered acidic soils P.W. Moody, R.L. Aitken, T. Dickson 537

83. Soybean yield and root growth as affected by lime rate and quality C.A. Rosolem, SJ. Bicudo, O.M. Marubayashi 543

84. Crop response to amendments on two high manganese soils in southeast Queensland T. Dickson, R.L. Aitken, P.w. Moody 549

85. Fertilizer and lime response in acid soils of Sumatra C.P. Mamaril, G.O. San Valentin, Erythryna Gustami, Z. Zaini, W.S. Diah 555

Contents XI

86. Response of round-leafed cassia (Cassia rotundifolia) to phosphorus, potassium and lime on ultisol soils in subtropical China D.L. Michalk, Huang Zhi-Kai 561

87. Effect of lime and sulphur on an acid alfisol and yield of cowpea (Vigna unguiculata (L.) Walp.) and sunflower (Helianthus annuus L.) in the semiarid tropics H.C. Parvathappa, H. Puttaswamy, T. Satyanarayana 565

88. Effect of liming an acidic Malaysian Ultisol on element concentrations in the soil solution and element uptake by corn and groundnut M. Norhayati, S. Siti Hawa, Mohd Yusoff Mohd Noor 569

89. Amelioration of acidity in subsurface soil using organic and inorganic calcium compounds CJ. Smith, K.M. Goh, WJ. Bond, J.R. Freney, S. Tuomi 573

90. The effect of different organic materials on the alleviation of Al toxicity in soybean on a red-yellow podzolic soil Arnoldus Klau Berek, B. Radjagukguk, Azwar Maas 579

*91. Effects of organic acid fractions extracted from Eucalyptus camaldulensis leaves on root elongation of maize (Zea mays) in the presence and absence of aluminium S.M. Harper, D.G. Edwards, G.L. Kerven, CJ. Asher 585

*92. Relationship between soil solution aluminium and low molecular weight organic acids in a conser­vation cropping system WJ. Slattery, G.R. Morrison 589

93. Evaluation of paper mill lime sludge as an acid soil amendment in Northeast Thailand P. Vityakon, S. Seripong 595

94. Changes in pH of a Florida citrus soil in response to basic slag and calcium hydroxide applications Heinz K. Wutscher 601

95. Long-term plant persistence on highly acidic soils amended with organic materials in two climatic zones AJ. Palazzo, C.R. Lee, R. Price 605

96. Effects of soil amendments on plant growth in pyritic soil R.A. Price, C.R. Lee, J.G. Skogerboe 611

97. Effects of silicic acid on the chemistry of monomeric and polymeric (AIl3) aluminium species in solutions P.L. Larsen, G.L. Kerven, L.c. Bell, D.G. Edwards 617

98. Effect of ionic strength on wheat yield in the presence and absence of aluminium D.M. Wheeler, D.C. Edmeades 623

99. Growth of sweet potato (Ipomoea batatas L.) as affected by pH in solution culture V.P. Ila'ava, CJ. Asher, EP.C. Blarney 627

100. Hydrogen ion inhibition of copper uptake by citrus seedlings A.K. Alva, E.Q. Chen 631

XII Contents

101. Acidity and phosphorus interactions: Some preliminary observations on rhizosphere soil P. Adamo, A.C. Edwards, MJ. Wilson 635

102. Liming effect of reactive phosphate rocks: A laboratory evaluation P. Loganathan, M.J. Hedley, S. Saggar 641

103. Use of phosphate rocks for sweet com production on a Malaysian Ultisol A.R. Zaharah, H.A.H. Sharifuddin 647

* 104. Effect of rock phosphate on soil properties and apparent phosphorus recovery in acid soil of Sumatra M. Utomo 653

105. Evaluation of soil tests for predicting pasture response on acid soils to phosphate supplied in water soluble and sparingly soluble forms S. Saggar, MJ. Hedley, R.E. White, P.E.H. Gregg, K.W. Perrott, I.S. Cornforth 657

SECTION 6: SOCIO-ECONOMIC ASPECTS OF ACID SOIL MANAGEMENT

106. Socio-economic aspects of acid soil management Emilio F. Moran 663

107. A socio-economic assessment of smallholder maize faftning on acid soils in Northern Mindanao, The Philippines 1.0. Mugot, R.A. Cramb 671

108. Socio-economic aspects of rubber intercropping on acid soils in Southern Thailand A. Masae, R.A. Cramb 679

109. A socio-economic assessment of land-use practices in a transmigration settlement on acid soils in South Kalimantan, Indonesia Masyhuri, R.A. Cramb 685

110. Socio-economic aspects of acid soil management and alternative landuse systems for north eastern states of India U.C. Sharma, R.N. Prasad 689

111. Socio-economic considerations in the planning of agroforestry systems for the acid uplands of northern Vietnam N.D. Tai, H.D. Nhan, N.T.Yen, D.M. Cameron 697

112. Longevity of liming in western Canada: Soil pH, crop yield and economics S.S. Malhi, G. Mumey, M. Nyborg, H. Ukrainetz, D.C. Penney 703

113. A group approach to improving understanding of soil acidity C.J. Hollier 711

114. Marketing soil acidity knowledge in Western Australia Karen Connell 717

Contents XIII

115. Acid soils: A farmer awareness program C. Dellavedova

SECfION 7: MANAGEMENT SYSTEMS FOR AGRICULTURE, HORTICULTURE AND FORESTRY ON ACID SOILS

116. Strategies for the management of soil acidity

723

RJ.K. Myers, E. De Pauw 729

117. Applying information from research on soil acidity through decision support systems I.G. Fenton, K.R. Helyar 743

118. Soil acidification and lime use in some agricultural systems in Queensland, Australia P.w. Moody, R.L. Aitken 749

119. Historical review of liming practices in Hokkaido, Northern Japan Mannosuke Saito, Toshio Sakuma 753

120. Management of acid soils for sustainable food crop production in the Philippines C.M. Duque Sr., R.B. Cagmat, N.P. Daquiado, A.R. Maglinao 757

121. Management of acid soils for opportunity food crop production in southern Thailand S. Suthipradit, L. Nualsri, P. Sophanodora, Y. Limchitti, N. Kungpisdan 761

122. Crop residue management for increasing production of pearl millet on acid sandy oil in Niger, West Africa H. Marschner, F.-P. Rebafka, H. Hafner, A. Buerkert 767

123. Acid upland soil in Vietnam and their management for agriculture Nguyen Tu Siem, Thai Phien 771

124. Rock phosphate and minimum tillage for management of acid soil in Sumatra M. Utomo, Sunyoto 775

125. Nitrogen supply from rotational or spatially zoned inclusion of Leguminosae for sustainable maize production on an acid soil in Indonesia Meine van Noordwijk, S.M. Sitompul, Kurniatum Hairiah, Endang Listyarini, Syekhfani Ms. 779

126. Soil acidification under nitrogen-fertilised pastures in tropical Australia M.A. Gilbert, G. Dickinson, P.w. Moody, D. Cooksley 785

127. The effects of soil pH on Cd concentration in wheat grain grown in south -eastern Australia D.P. Oliver, K.G. Tiller, M.K. Conyers, WJ. Slattery, R.H. Merry, A.M. Alston 791

128. Acid soil management in orchard soils of the South Western Cape Province, South Africa J. Wooldridge, W.A. Kotze, M.E. Joubert 797

129. Effect of low soil pH from different fertilisers on performance of apple and pear trees 1. Thomas Raese 803

XIV Contents

130. Effects of NK fertiliser on soil pH and exchangeable K status on acid soils in an oil palm plantation in Malaysia Khan Kiang Kee, Kah Joo Goh, Poh Soon Chew 809

131. Aluminium species and pH in soil solution under different crops R.L. Parfitt, H.J. Percival, G. van der Lee 817

Second International Symposium on Plant-Soil Interactions at Low pH

Financial support by the following organizations is gratefully acknowledged:

Australian International Development Assistance Bureau (AIDAB) Department of Agriculture, The University of Queensland Incitec Ltd Queensland Government Wool Research and Development Corporation Grains Research and Development Corporation Sugar Research and Development Corporation International Science Foundation, New York Australian Tourist Commission Australian Society of Soil Science (Queensland Branch) Limestone Association of Australia QANTAS Ansett Australia Australian Society of Soil Science

Thanks are also extended to the following organizations who provided assistance:

Australian Centre for International Agricultural Research (ACIAR) The Hyatt Regency, Coolum CSIRO Division of Tropical Crops and Pastures Bureau of Sugar Experiment Stations

International Steering Committee Plant-Soil Interactions at Low pH (as of 1 October 1993)

Chairman: David G. Edwards, Australia

Members: Bryon W. Bache, United Kingdom Keith G. Briggs, Canada Ronny R. Duncan, United States of America Douglas C. Edmeades, New Zealand Nand K. Fageria, Brazil Martin P.W. Farina, South Africa Walter J. Horst, Germany Willem G. Keltiens, The Netherlands R. Paul Murrmann, United States of America Meine van Noordwijk, Indonesia Shivaji Pandey, Colombia Geraldine S.P. Ritchie, Australia Masahiko Saigusa, Japan Pedro A. Sanchez, Kenya Robert E. Schaffert, Brazil Malcolm E. Sumner, United States of America Gregory J. Taylor, Canada Tadao Wagatsuma, Japan

Second International Symposium on Plant·Soil Interactions at Low pH

Organizing Committee

David G. Edwards Robin C. Bruce Phil W. Moody

- Chairman - Deputy Chairman - Secretary - Treasurer - Program - Publication - Tours - Local Arrangements

F. Pax C. Blamey L. Clive Bell Richard A. Date Robert L. Aitken Eoin S. Walls Robert T. Mullins Graham Kingston

- Member (to 9 June 1992) - Member (from 9 June 1992)

Symposium Managers

Australian Convention and Travel Services Pty Ltd G.P.O. Box 2200 Canberra, ACT 2601, Australia

Ms Anette Palm Ms Sally Clark

Keynote Speakers

Ernst Mutert, Singapore Geraldine S.P. Ritchie, Australia James M. Lynch, United Kingdom Patrick Lavelle, France Douglas C. Edmeades, New Zealand Gregory J. Taylor, Canada Shivaji Pandey, Colombia Emilio F. Moran, United States of America Robert J.K. Myers, Thailand

Session Chairpersons

L. Clive Bell, Australia Bryon W. Bache, United Kingdom Richard A. Date, Australia R. Paul Murrmann, United States of America Peter J. Randall, Australia Malcolm E. Sumner, United States of America Peter N. Vance, Australia Willem G. Keltjens, The Netherlands

R.A. Date eta/. (eds.), Plant Soil Interactions at Low pH, 1,1995. © 1995 Kluwer Academic Publishers.

Preface

Acid soils limit agricultural production throughout the world; their management is reliant upon a thor­ough understanding of plant-soil relationships at low pH. Improved agricultural management practices, that include the use of legumes and/or the input of nitroge­nous fertilizers and acid rain, have increased acid inputs into ecosystems. This has heightened the con­cern about soil acidity problems in many countries, both developed and lesser-developed. A major focus at present centers upon the sustainability of agricul­tural production systems being used by fanners who cultivate acid soils for their livelihood. There is a need to develop sustainable systems in many instances.

Scientists from Alberta, Canada, recognized the need to provide a forum that would enable scientists with different disciplinary interests to exchange infor­mation and ideas on solving problems of plant growth in acid soils. As a result of their efforts, the First Inter­national Symposium on Plant-Soil Interactions at Low pH was held at Grande Prairie, Alberta, Canada in July 1987. At that Symposium, 109 participants from 13 countries presented 45 oral and 30 poster papers. The proceedings of the symposium were published as a special issue of the journal "Communications in Soil Science and Plant Analysis". Symposium partici­pants agreed that further symposia should be held every three to four years. A 13 member International Steer­ing Committee was appointed to assist in the planning of the Second Symposium. They chose the USDA­Appalachian Soil and Water Conservation Research Laboratory in Beckley, West Virginia as the host for the Second Symposium.

The Second International Symposium on Plant-Soil Interactions at Low pH was held at Pipestem Resort State Park, West Virginia, USA in June 1990. It was attended by 220 delegates from 28 countries. At that Symposium, 11 invited reviews, 38 oral papers and about 160 poster papers were presented. The pro­ceedings of the Symposium were subsequently pub­lished by Kluwer Academic Publishers, Dordrecht, The Netherlands as "Plant-Soil Interactions at Low

pH". In addition, a selection of papers from the Sym­posium was published as a special issue of the journal "Plant and Soil". The International Steering Commit­tee chose Queensland, Australia as the host site for the Third Symposium.

The Third International Symposium on Plant-Soil Interactions at Low pH was held at The Hyatt Regency, Coolum, Queensland, Australia from 12 to 16 Septem­ber 1993. It was attended by 208 delegates from 32 countries. At that symposium, 9 invited review papers, 55 contributed oral papers and 121 poster papers were presented. The major themes covered in the sessions included chemistry and physics of acid soils, microbial and faunal activity in acid soils, mechanisms of acid tolerance of plants, selection and breeding of acid­tolerant plants, diagnosis and correction of acid soil infertility, socio-economic aspects of acid soil manage­ment, and management systems for agriculture, horti­culture and forestry on acid soils. The present Proceed­ings contain 131 refereed papers from the Third Sym­posium. The 9 review papers and the research papers report contemporary research on plant-soil interactions at low pH.

The Fourth International Symposium on Plant-Soil Interactions at Low pH will be held in Belo Hori­zonte, Brazil in September 1996. The Chairman of the Organizing committee for that symposium is Dr Robert E. Schaffert, CNPMSIEMBRAPA, Caixa Postal 151, 35701-970 Sete Lagoas, MG, Brazil.

R.A. Date N.J. Grundon M.E. Probert

G.E. Rayment D.G. Edwards